Materials suitable for protective garments for wear in rain, in handling hazardous chemicals or in situations where the environment must be protected from being contaminated by the wearer (i.e. clean rooms) while the wearer must also be protected from hazardous chemicals ideally should keep the wearer dry by preventing leakage of water or fluids into the garment and by allowing perspiration to evaporate from the wearer to the outside of the garment.
A variety of water-proof, breathable materials are known. Fabrics treated with silicones, fluorocarbons and other water repellent treatments usually are breathable, allowing perspiration to evaporate, but they offer marginal waterproofness. They frequently allow water leakage under very low pressures and they typically allow spontaneous leakage after mild abrasion or mechanical flexing. Non-elastic polytetrafluoroethylene (PTFE) based materials have, in large part, replaced treated fabrics for protective garment applications as the PTFE materials have excellent breathability and waterproof properties decidedly superior to the treated materials. Most recently, PTFE based materials having elastomeric properties have been introduced to the market which offer improved wearer comfort relative to the non-elastic PTFE materials.
According to the Encyclopedia of Textiles, third edition, pages 310 to 315, there are two categories of stretch fabrics, the categories being based on the degree of stretchability of the fabric. They are: (1) Power or Action Stretch and (2) Comfort Stretch.
"Power Stretch or Action Stretch," as the names imply, provide a fabric with a high degree of extensibility and quick recovery. The stretch factor generally ranges from at least 30 to 50 percent or more with no more than 5 to 6 percent loss in recovery. Such stretch fabrics are best adapted to ski wear, foundation garments, swim wear, athletic clothing and professional types of active sport wear.
Comfort Stretch applies to fabrics with less than 30 percent stretch factor and no more than 3 to 5 percent loss in recovery. Such fabrics are used in clothing for everyday wear which need only a moderate degree of elasticity.
The clothing industry is using stretch fabrics more extensively for garments where flexibility of movement is essential; for example in athletic garments, running suits, exercise suits, ski wear, etc. More recently, these fabrics have also been utilized for protective garments where the stretch properties of the fabric allow for a closer fitting garment without adversely effecting the wearer's comfort.
U.S. Pat. No. 4,187,390 (Gore) describes a polytetrafluoroethylene polymer in a porous form which has an amorphous content exceeding about 5% and which has a microstructure characterized by nodes interconnected by fibrils. The material has high porosity and high strength. It can be used to produce shaped articles such as tubes, rods and continuous fibers. Laminations can be employed and impregnation and bonding can be readily used to produce a large variety of articles. Compressed articles of very high strength can also be produced from these porous forms. A wearable fabric using such a bonded laminate is sold under the name GORE-TEX.TM.. These GORE-TEX fabrics are not considered elastic fabrics.
U.S. Pat. No. 4,443,511 (Worden et al.) describes a water-proof and breathable elastomeric polytetrafluoroethylene layered article for use in, for example, material for protective articles. The waterproof and breathable polytetrafluoroethylene layered article can exhibit elastomeric properties of stretch to break of 275% in the longitudinal direction and 145% in the transverse direction and a total stretch recovery of at least 39% after being stretched to 75% extension for 100 cycles. The invention further provides a waterproof and breathable elastomeric polytetrafluoroethylene layered article bonded to a stretch fabric. The waterproof and breathable elastomeric polytetrafluoroethylene layered article bonded to a stretch fabric is thus durable and possesses a moisture vapor transmission rate exceeding 1000 gm/m.sup.2 /24 hours, and preferably above 2000 gm/m.sup.2 /24 hours. The materials of this invention exhibit comparatively poor stretch recovery properties.
U.S. Pat. No. 4,539,255 (Sato et al.) describes a moisture-permeable waterproof fabric which comprises a polyamino acid modified polyurethane film having a thickness of 2 to 20 microns and a fabric bonded on the polyurethane film by a polyurethane adhesive in an amount of at least 10 gm/m.sup.2. The polyamino acid modification ratio of the polyurethane film is within the range of 2 to 20%. The total amount of the adhesive and the polyurethane film is not more than 50 gm/m.sup.2. The fabrics of this invention are not considered elastic fabrics.
U.S. Pat. No. 4,692,369 (Nomi) describes a water-vapor-permeable waterproof, highly elastic film of expanded, porous, unsintered polytetrafluoroethylene having impregnated within the pores of the porous film, on both sides thereof, a water-vapor-permeable resin, for example, an elastomer containing urethane bonds and hydrophilic group(s) in its molecular structure. The film of the invention is useful in clothing, tents, and various applications where water vapor transmission characteristics and waterproofness are simultaneously desired. The film has elongation percentage in at least one direction exceeding 40% and durability in repeated stretching to 80% of its elongation percentage of more than 200,000 cycles. The materials of this invention are films and the elongation and recovery properties of the films are too low for garment applications requiring comfort stretch properties.
U.S. Pat. No. 4,761,324 (Rautenberg et al.) describes a laminated elastic fabric which includes a layer of stretch material having substantial elastic qualities, a polymer film layer being breathable, water-resistant and having elastic qualities, and an adhesive being present in substantially discontinuous segments bonding the film to the elastic fabric. The polymer film component of the fabrics of this invention has elastic properties.